1. Field of the Invention
This invention relates to Bluetooth™ and 802.11 wireless communication systems, and more particularly to a method and apparatus for operating a dual-mode radio in a wireless communication system.
2. Description of Related Art
Wireless communication systems facilitate high-speed connectivity and data and voice transport from point-to-point and point-to-multipoint bases. Exemplary wireless communication systems include “Bluetooth™ protocol” systems that facilitate the transport of data between Bluetooth™ devices such as wireless headsets, cellular phones, laptop computers and personal digital assistants (PDAs), and “IEEE 802™ protocol” systems that facilitate the transport of data over wireless local area networks (WLANs), which include devices such as desktop and laptop computers.
As is well known, Bluetooth™ is a global specification standard for radio communications operating at 2.4 GHz radio frequencies. Bluetooth™ devices (i.e., those that comply with the Bluetooth™ Specification) replace normal cable connections using short-range radio links.
Bluetooth™ protocol technology is featured in cordless telephony, intercom, FAX and LAN access, and dial-up networking applications. Bluetooth™ wireless communication protocols are implemented in wireless headsets, cellular phones, PDAs, printers, and other mobile devices. Bluetooth™ technology is described in more detail in a specification produced by the Bluetooth™ Special Interest Group (SIG), entitled “Specification of the Bluetooth™ version 1.1”, electronically available to the public via the well-known Internet at <http://www.Bluetooth.com>, published on Feb. 22, 2001, referred to herein as the “Bluetooth™ Specification”, and incorporated for reference herein in its entirety for its teachings on Bluetooth™ flow control, signals, devices and communication protocols and schemes.
In addition to the Bluetooth™ communications protocol, various IEEE 802.11 communication protocols (referred to hereinafter as “802.11”) exist for radio communications operating at 2.4 GHz radio frequencies. One exemplary well-known IEEE 802.11 communications protocol is the IEEE 802.11b protocol (referred to hereinafter as “802.11b”). The 802.11b protocol allows 802.11b devices (i.e., those that comply with the 802.11b standard) to operate at high data transmission rates (e.g., 11 Mbps). The 802.11b protocol is particularly useful in implementing Wireless Local Area Networks (WLANs). 802.11b devices are described in more detail in a standard produced by the IEEE 802 Working Group, entitled “IEEE Std 802.11b-1999”, electronically available to the public via the well-known Internet at <http://standards.ieee.org>, referred to herein as the “802.11b Specification”, and incorporated for reference herein in its entirety for its teachings on 802.11b flow control, signals, devices and communication protocols and schemes.
Another exemplary IEEE 802.11 communications protocol is the newly emerging IEEE 802.11 g. Some embodiments of the invention are described below using the IEEE 802.11b protocol as an exemplary communications protocol. However, this is not meant as a limitation to the present invention as the present inventive method and apparatus contemplates use of any of the IEEE 802.11 communication protocols and future variants. Therefore, the generic “IEEE 802.11” term used below encompasses all IEEE 802.11 communication protocols.
Most 802.11b devices use at least two antennas to provide an “antenna diversity” function in the receiver. As is well known, antenna diversity is used to compensate for the detrimental effects of signal path loss (e.g., multipath fading, reflections, and absorption). Antenna diversity requires use of at least two antennas. In accordance with well-known antenna diversity techniques, receivers measure the signal quality of multiple antennas and select (for the transmission and reception of data) the antenna having the best signal quality. In contrast to 802.11 devices, Bluetooth™ devices typically use only one antenna because the communication schemes used by the Bluetooth m devices are less prone to signal path loss.
Because both Bluetooth™ and 802.11 devices are widely used and readily available, it is desirable to operate both Bluetooth™ and 802.11 devices within close proximity to one another. This is especially true when the devices are used in implementing a single common communications device. For example, a laptop can include both a Bluetooth™ protocol device for wireless communication with a Bluetooth™ wireless mouse, and an 802.11 protocol device for wireless communication with an 802.11 WLAN access point.
Disadvantageously, heretofore when Bluetooth™ and 802.11 protocol devices operate in close proximity, interference can be produced adversely affecting communication using both protocols. Interference occurs because both protocols operate on the 2.4 GHz ISM frequency band. Specifically, over-air interference and saturation of one transmitter by another transmitter can occur when a Bluetooth™ antenna is in close proximity (e.g., within one-half meter) of an 802.11 antenna. As is well known, interference increases the probability of reception errors. In any data communication system, it is desirable to reduce the probability reception errors.
Saturation of Bluetooth™ devices can occur because the Bluetooth™ protocol requires RF transmit powers of 1 mW, whereas, the 802.11 protocol requires RF transmit powers of 30 to 100 mW. Thus, when an 802.11 transceiver operates within close proximity to a Bluetooth™ device, the 802.11 transmit signals can increase the receiver signal levels so that Bluetooth™ front-end circuits are driven into non-linear ranges. This can decrease Bluetooth™ reception quality. In certain situations, the 802.11 transmit signals are sufficiently strong to cause physical damage to the Bluetooth™ devices.
A need therefore exists for a dual-mode radio method and apparatus that uses devices operating in conformance with the Bluetooth™ and 802.11 communication protocols. The method and apparatus should prevent saturation of the Bluetooth™ protocol devices. The present invention provides such a dual-mode radio method and apparatus.